Nuclear medicine imaging systems and methods having detector heads with two collimators

ABSTRACT

A radiation detector head assembly includes a detector column. The detector column includes a detector having a first surface and a second surface opposite the first surface. The detector column also includes a first collimator disposed over the first surface of the detector configured for use during imaging scans involving radiation in a first energy range. The detector column further includes a second collimator disposed over the second surface of the detector configured for use during imaging scans involving radiation in a second energy range different from the first energy range.

BACKGROUND

The subject matter disclosed herein relates to medical imaging systems and, more particularly, to radiation detection systems.

In nuclear medicine (NM) imaging, such as single photon emission computed tomography (SPECT), radiopharmaceuticals are administered internally to a patient. Detectors (e.g., gamma cameras), typically installed on a gantry, capture the radiation emitted by the radiopharmaceuticals and this information is used, by a computer, to form images. The NM images primarily show physiological function of, for example, the patient or a portion of the patient being imaged.

An NM imaging system may be configured as a multi-head imaging system having several individual detectors distributed about the gantry. Each detector (e.g., detector head) may pivot or sweep to provide a range over which the detector may acquire information that is larger than a stationary field of view of the detector. Detectors in nuclear medicine need to absorb x- or gamma-ray photons over a wide energy range. Depending on the application (low/medium energy versus high energy), a different collimator may be utilized for collimation. However, changing out the collimator for each detectors typically involves utilizing a mechanical exchange process to manually replace one collimator utilized with one application with another collimator utilized for another application. Utilization of the mechanical exchange process may be a time consuming process that may take several minutes resulting in down time that hampers workflow (e.g., hospital patient flow).

BRIEF DESCRIPTION

A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

In one embodiment, a radiation detector head assembly is provided. The radiation detector head assembly includes a detector column. The detector column includes a detector having a first surface and a second surface opposite the first surface. The detector column also includes a first collimator disposed over the first surface of the detector configured for use during imaging scans involving radiation in a first energy range. The detector column further includes a second collimator disposed over the second surface of the detector configured for use during imaging scans involving radiation in a second energy range different from the first energy range.

In another embodiment, a nuclear medicine multi-head imaging system is provided. The system includes a gantry defining a bore configured to accept an object to be imaged, wherein the gantry is configured to rotate about the bore. The system also includes a plurality of detector units mounted to the gantry and configured to rotate with the gantry around the bore in rotational steps, each detector unit configured to sweep about a corresponding axis and acquire imaging information while sweeping about the corresponding axis. Each detector unit includes a detector head. The detector head includes a detector column. The detector column includes a detector having a first surface and a second surface opposite the first surface. The detector column also includes a first collimator disposed over the first surface of the detector configured for use during imaging scans involving radiation in a first energy range. The detector column further includes a second collimator disposed over the second surface of the detector configured for use during imaging scans involving radiation in a second energy range different from the first energy range.

In a further embodiment, a method for changing a collimator in a detector head of a nuclear medicine (NM) multi-head imaging system is provided. The method includes receiving an input to change the collimator in the detector head of the NM multi-head imaging system. The method also includes rotating a detector column from a first position to a second position or a second position to a first position in response to the input, wherein the detector column includes a detector having a first surface and a second surface opposite the first surface, a first collimator disposed over the first surface of the detector configured for use during imaging scans involving radiation in a first energy range, and a second collimator disposed over the second surface of the detector configured for use during imaging scans involving radiation in a second energy range different from the first energy range.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present subject matter will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic view of an embodiment of a nuclear imaging system, in accordance with aspects of the disclosed techniques;

FIG. 2 is a schematic view of a detector arrangement, in accordance with aspects of the disclosed techniques;

FIG. 3 is a schematic view of sweep and acquisition ranges for a detector unit, in accordance with aspects of the disclosed techniques;

FIG. 4 is schematic view of an embodiment of a detector head, in accordance with aspects of the disclosed techniques;

FIG. 5 is a cross-sectional view of the detector head in FIG. 4 , in accordance with aspects of the disclosed techniques;

FIG. 6 is a schematic view illustrating switching between usage of different collimators within a detector head assembly, in accordance with aspects of the disclosed techniques;

FIG. 7 is a flow chart of an embodiment of a method for switching between collimators in a detector head assembly, in accordance with aspects of the disclosed techniques; and

FIG. 8 is a schematic view of an imaging system, in accordance with aspects of the disclosed techniques.

DETAILED DESCRIPTION

One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the present subject matter, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Furthermore, any numerical examples in the following discussion are intended to be non-limiting, and thus additional numerical values, ranges, and percentages are within the scope of the disclosed embodiments.

The present disclosure provides systems and methods for utilizing at least two collimators within a radiation detector head assembly of a nuclear medicine (NM) multi-head imaging system. In particular, each detector head of the NM multi-head imaging system includes a detector column that includes a semiconductor detector having a first surface that includes a cathode and a second surface that includes pixelated anodes, where a respective collimator is disposed over both the first surface and the second surface of the semiconductor detector. The collimator disposed over the cathode is configured for utilization during an imaging scan involving radiation in a first energy range (e.g., low energy range of approximately 40 to 300 keV) and the collimator disposed over the pixelated anodes is configured for utilization during an imaging scan involving radiation in a second energy range (e.g., high energy range of approximately 250 to 400 keV) different from the first energy range. The first and second energy ranges may partially overlap (e.g., at a high end of the first energy range and a low end of the second energy range) but differ in extent. Rotation about a longitudinal axis (e.g., sweeping axis) of the detector head (e.g., via a motor) enables the collimators to be interchanged between scans or during the same scan (e.g., dual isotopes applications) involving different levels of energy (e.g., low energy versus high energy). The disclosed embodiments enable the automatic interchange between the different collimators to occurs within a matter of seconds (e.g., as opposed to minutes). The interchange occurs completely within the radiation detector head assembly (without having to remove one of the collimators or mounting the collimator to be utilized) and without the utilization of a mechanical (and manual) collimator exchange process. The quick automatic exchange between collimators saves time during the day and avoids downtime for the imaging system, thus, enabling an improved workflow (e.g., hospital patient flow). The disclosed embodiments may also reduce the cost of the imaging system.

FIG. 1 provides a schematic view of a NM multi-head imaging system 100 in accordance with various embodiments. Generally, the imaging system 100 is configured to acquire imaging information or data (e.g., photon counts) from an object to be imaged (e.g., a human patient) that has been administered a radiopharmaceutical. The depicted imaging system 100 includes a gantry 110 and a processing unit 120.

The gantry 100 defines a bore 112. The bore 112 is configured to accept an object to be imaged (e.g., a human patient or portion thereof). As seen in FIG. 1 , a plurality of detector units 115 are mounted to the gantry 110. In the illustrated embodiment, each detector unit 115 includes an arm 114 and a head 116. The arm 114 is configured to articulate the head 116 radially toward and/or away from a center of the bore 112 (and/or in other directions), and the head 116 includes at least one detector, with the head 116 disposed at a radially inward end of the arm 114 and configured to pivot to provide a range of positions from which imaging information is acquired.

The detector of the head 116, for example, may be a semiconductor detector. For example, a semiconductor detector in various embodiments may be constructed using different materials, such as semiconductor materials, including Cadmium Zinc Telluride (CdZnTe), often referred to as CZT, Cadmium Telluride (CdTe), and Silicon (Si), among others. In certain embodiments, the detector of the head 116 may include a scintillator with a silicon photomultiplier (SiPM). The detector may be configured for use with, for example, nuclear medicine (NM) imaging systems such as single photon emission computed tomography (SPECT) imaging systems.

In various embodiments, the detector may include an array of pixelated anodes, and may generate different signals depending on the location of where a photon is absorbed in the volume of the detector under a surface if the detector. The absorption of photons from certain voxels corresponding to particular pixelated anodes results in charges generated that may be counted. The counts may be correlated to particular locations and used to reconstruct an image.

In various embodiments, each detector unit 115 may define a corresponding view that is oriented toward the center of the bore 112. Each detector unit 115 in the illustrated embodiment is configured to acquire imaging information over a sweep range corresponding to the view of the given detector unit. FIG. 2 illustrates a detector arrangement 200 in accordance with various embodiments. The detector units of FIG. 1 , for example, may be arranged in accordance with aspects of the detector arrangement 200. In some embodiments, the system 100 further includes a CT (computed tomography) detection unit 140. The CT detection unit 140 may be centered about the bore 112. Images acquired using both NM and CT by the system are accordingly naturally registered by the fact that the NM and CT detection units are positioned relative to each other in a known relationship. A patient may be imaged using both CT and NM modalities at the same imaging session, while remaining on the same bed, which may transport the patient along the common NM-CT bore 112.

As seen in FIG. 2 , the detector arrangement 200 includes detector units 210(a), 210(b), 210(c), 210(d), 210(e), 210(f), 210(g), 210(h), 210(i), 210(j), 210(k), 210(l) disposed about and oriented toward (e.g., a detection or acquisition surface of the detector units, and/or the FOV (Field of View), are oriented toward) an object 202 to be imaged in the center of a bore. Each detector unit of the illustrated embodiment defines a corresponding view that may be oriented toward the center of the bore of the detector arrangement 200 (it may be noted that because each detector unit may be configured to sweep or rotate about an axis, the FOV need not be oriented precisely toward the center of the bore, or centered about the center of the bore, at all times). The view for each detector unit 210, for example, may be aligned along a central axis of a corresponding arm (e.g., arm 114) of the detector unit 210. In the illustrated embodiment, the detector unit 210(a) defines a corresponding view 220(a), the detector unit 210(b) defines a corresponding view 220(b), the detector unit 210(c) defines a corresponding view 220(c), and so on. The detector units 210 are configured to sweep or pivot (thus sweeping the corresponding FOV's) over a sweep range (or portion thereof) bounded on either side of a line defined by the corresponding view during acquisition of imaging information. Thus, each detector unit 210 may collect information over a range larger than a field of view defined by a stationary detector unit. It may be noted that, generally, the sweeping range over which a detector may potentially pivot may be larger than the corresponding view during acquisition. In some cameras, the sweeping range that a detector may pivot may be unlimited (e.g., the detector may pivot a full 360 degrees or less), while in some embodiments the sweeping range of a detector may be constrained, for example over 180 degrees (from a −90 degree position to a +90 degree position relative to a position oriented toward the center of the bore). It may be noted that the detector units 210 of FIG. 2 are mounted to a gantry (e.g., gantry 100 in FIG. 1 ). The gantry may be rotatable to different positions, with the detector units 210 rotating with the gantry.

With continued reference to FIG. 1 , the depicted processing unit 120 is configured to acquire imaging information or data (e.g., photon counts) via the detector units 115. In various embodiments the imaging information includes focused imaging information and background imaging information. The focused imaging information corresponds to a focused region, and the background imaging information corresponds to tissues surrounding the focused region. As used herein, both the focused region and surrounding tissue may be used for imaging and/or diagnostic purposes; however, the focused region may be more pertinent or useful for diagnostic purposes, and, accordingly, more imaging information is acquired for the focused region than for the surrounding tissue. An example of a focused region and surrounding tissue is shown in FIG. 3 .

FIG. 3 depicts a focused region and surrounding tissue of an object, or a focused portion and background portion of an image. As seen in FIG. 3 , the detector unit 300 includes a detector head 310 disposed at an end of a detector arm 308. In FIG. 3 , only one detector unit 300 is depicted for ease and clarity of illustration. It may be noted that the detector unit 300 may be part of an arrangement of plural detector heads, such as depicted in FIGS. 1 and 2 , and that the general principles discussed in connection with the detector unit 300 may be applied to one or more additional detector units of a multi-head camera imaging system. In FIG. 3 , the detector unit 300 may be used to acquire imaging information (e.g., photon counts) of an object 303 having a focused region 302. In the illustrated embodiment, the focused region 302 is surrounded by surrounding tissue 322. The focused region 302, for example, may be an organ such as the heart or brain (or portion thereof), and may have a substantially larger uptake of an administered radiopharmaceutical than surrounding tissue 322 of the object 303. For example, in some embodiments, the focused region 302 is the striata of the brain, and the surrounding tissue 322 includes other portions of the brain. A ratio of detected activity between the striata and other portions of the brain may be used in analyzing whether or not a patient has Parkinson's disease. A central axis 312 of the detector unit 300 passes through a center 304 of the focused region 302 (which is disposed at the center of a bore in the illustrated embodiment). It may be noted that in various embodiments the central axis or center view of the detector need not necessarily pass through the focus center or through the focused region. The central axis 312, for example, may correspond to a line along the view corresponding to the detector unit 300 when the detector unit 300 is at a midpoint of a range of coverage of the detector unit 300, and/or may be aligned with a central axis of the detector arm 308 to which the detector head 310 is attached.

In the illustrated embodiment, the detector unit 300 is depicted as aligned with the central axis 312, and may be rotated, pivoted or swept over a sweep range 309 between a first limit 313 and a second limit 314. In the illustrated embodiment, the first limit 313 and the second limit 314 define a sweep range 309 (or maximum range of coverage) of 180 degrees. In other embodiments, the sweep range 309 and/or relative positions of the first limit 313 and second limit 314 may vary from the depicted arrangement. It may be noted that the sweep range 309 provides more coverage than is required to collect imaging information of the focused region 302 and the surrounding tissue 322. Thus, if the detector unit 300 is swept over the sweep range 309 during a duration of an imaging acquisition, information that may be not be useful for diagnostic purposes (e.g., information towards the ends of the sweep range 309 that does not include information from either the focused region 302 or the surrounding tissue 322) may be collected. The time used to collect the information that is not useful for diagnostic purposes may be more efficiently spent collecting additional information from the focused region 302 and/or the surrounding tissue 322. Accordingly, in the illustrated embodiment, the detector unit 310 may be controlled (e.g., by processing unit 120) to be swept or pivoted over an acquisition range 320 (e.g., a range including the focused region 302 and surrounding tissue 322) instead of over the entire sweep range 309 during acquisition of imaging information.

As seen in FIG. 3 , the acquisition range 320 generally corresponds to edges of the surrounding tissue 322, and is bounded by a first boundary 317 and a second boundary 318. A focused range 321 is defined within the acquisition range 320 and corresponds to edges of the focused region 302. The focused range 321 is bounded by a first boundary 315 and a second boundary 316. Generally, more imaging information is acquired over the focused range 321 than over the background portions 330 of the acquisition range 320 which include the surrounding tissue 322 but not the focused region 302. Generally, more time is spent acquiring information over the focused range 321 than over the background portions 330. For example, the detector 310 may be swept at a higher sweep rate over the background portions 330 when acquiring the background imaging information than over the focused range 321 when acquiring the focused imaging information. The first boundary 315 is located at an angle α in clockwise direction from the central axis 312 (and, in the illustrated embodiment, from the center 304). The second boundary 316 is located at an angle β in a counterclockwise direction from the central axis 312 (and, in the illustrated embodiment, from the center 304).

It may be noted the boundaries may not necessarily correspond to a central axis or portion of a field of view of the detector unit, but may correspond to an edge or other portion of the field of view. Further, the acquisition range 320 may be configured in various embodiments to include more or less surrounding tissue beyond the focused region. Further, the acquisition range 320 may include an amount of background or surrounding tissue for a first phase of an acquisition period and omit background or surrounding tissue for a second phase; or omit the acquisition of surrounding tissue altogether (for one or several detector units comprising the system).

Returning to FIG. 1 , in various embodiments the processing unit 120 includes processing circuitry configured to perform one or more tasks, functions, or steps discussed herein. It may be noted that “processing unit” as used herein is not intended to necessarily be limited to a single processor or computer. For example, the processing unit 120 may include multiple processors, FPGA's, ASIC's and/or computers, which may be integrated in a common housing or unit, or which may distributed among various units or housings (e.g., one or more aspects of the processing unit 120 may be disposed onboard one or more detector units, and one or more aspects of the processing unit 120 may be disposed in a separate physical unit or housing). The processing unit 120, for example, may switch between different collimators (e.g., configured for different energy applications) depending on the energy application, determine acquisition range boundaries for focused and background regions, control the detector heads to acquire desired amounts of focused and background information, and reconstruct an image as discussed herein. It may be noted that operations performed by the processing unit 120 (e.g., operations corresponding to process flows or methods discussed herein, or aspects thereof) may be sufficiently complex that the operations may not be performed by a human being within a reasonable time period. For example, identifying boundaries of acquisition ranges, providing control signals to detector units, reconstructing images, or the like may rely on or utilize computations that may not be completed by a person within a reasonable time period.

In the illustrated embodiment, the processing unit 120 includes a reconstruction module 122, a control module 124, and a memory 130. It may be noted that other types, numbers, or combinations of modules may be employed in alternate embodiments, and/or various aspects of modules described herein may be utilized in connection with different modules additionally or alternatively. Generally, the various aspects of the processing unit 120 act individually or cooperatively with other aspects to perform one or more aspects of the methods, steps, or processes discussed herein.

In the illustrated embodiment, the depicted reconstruction module 122 is configured to reconstruct an image. The depicted control module 124 is configured to interchange or switch between different collimators (e.g., configured for different energy applications) depending on the energy application. In addition, the depicted control module 124 is configured to control the detector heads 116 to sweep over corresponding acquisition ranges to acquiring focused imaging information and background imaging information. It may be noted that, in various embodiments, aspects of the control module 124 may be distributed among detector units 115. For example, each detector unit may have a dedicated control module disposed in the head 116 of the detector unit 115.

The memory 130 may include one or more computer readable storage media. The memory 130, for example, may store information describing previously determined boundaries of acquisition ranges, parameters to be utilized during performance of a scan, parameters to be used for reconstruction or the like. Further, the process flows and/or flowcharts discussed herein (or aspects thereof) may represent one or more sets of instructions that are stored in the memory 130 for direction of operations of the imaging system 100.

It may be noted that while the processing unit 120 is depicted schematically in FIG. 1 as separate from the detector units 115, in various embodiments, one or more aspects of the processing unit 120 may be shared with the detector units 115, associated with the detector units 115, and/or disposed onboard the detector units 115. For example, in some embodiments, at least a portion of the processing unit 120 is integrated with at least one of the detector units 115.

FIG. 4 is a schematic view of an example detector head 400 (e.g., having two collimators for different energy applications) and FIG. 5 is a cross-sectional view (e.g., axial cross section) of the detector head 400. As seen in FIG. 5 , the detector head 400 includes a stepper motor 402 that may be utilized to pivot a detector column 404 about its longitudinal axis 406 (e.g., sweeping axis). It may be noted that motors other than stepper motors may be used in various embodiments. The detector head 400 also includes a gear 408 coupling the stepper motor to the column 404, as well as a slip ring 410 (configured to allow for transfer of signals between the rotating detector column 404 and non-rotating components) and a multiplex board 412. In the illustrated embodiment, the detector head 400 also includes an air channel 414 configured to provide cooling to components of the detector head 400.

As depicted in FIG. 5 , the detector column 404 includes a detector 416 (e.g., semiconductor detector such as CZT detector). The detector 416 includes a first surface 418 having a cathode disposed on it and a second surface 420 having pixelated anodes disposed on it. The detector column 404 includes collimators 422, 424 disposed over both the first surface 418 and the second surface 420 of the semiconductor device, respectively. The collimator 422 disposed over the cathode is configured for utilization during an imaging scan involving radiation in a first energy range (e.g., low energy range of approximately 40 to 300 keV). The collimator 424 disposed over the pixelated anodes is configured for utilization during an imaging scan involving radiation in a second energy range (e.g., high energy range of approximately 250 to 400 keV) different from the first energy range. The terms “high” and “low” as utilized herein are relative, with high energy meaning an energy higher than another energy and low energy meaning an energy lower than another energy. As noted above, the first and second energy ranges may partially overlap (e.g., at a high end of the first energy range and a low end of the second energy range) but differ in extent. As noted above, the collimators 422, 424 may be utilized during the same scan involving dual isotopes (e.g., high and low energy isotopes).

The collimators 422, 424 each have a respective height 426, 428 (e.g., height for the septa). In certain embodiments, the height 428 of the collimator 424 is greater than the height 426 of the collimator 422. In certain embodiments, the ratio of the height 428 to the height 426 may range from 2:1 to 5:4. For example, the ratio of the height 428 to the height 426 may be 2:1, 3:2, 4:3, 5:4, or another ratio. In certain embodiments, the heights 426, 428, of the collimators 422, 424 may be the same. Due to limited space within the detector head 400, the heights 426, 428 of the collimators are limited. In order to avoid degraded spatial resolution due to a limited height collimator and to improve image quality (e.g., due to increased sensitivity, resolution, and/or contrast), sub-pixelation (e.g., either real or virtual sub-pixelation) may be utilized as described in U.S. Pat. No. 10,761,224, entitled “Systems and Methods for Improved Detector Assembly Sizing,” issued on Sep. 1, 2020, and incorporated by reference in its entirety.

The detector column 404 includes a radiation shield 430 (e.g., lead shield). In certain embodiments, the radiation shield is an aluminum extrusion having lead. The radiation shield 430 includes a first radiation shield portion 432 and a second radiation shield portion 434 that flank the collimators 422, 424, the detector 416, and associated electronics. In particular, the radiation shield portions 432, 434 extend from adjacent end 436 of the collimator 422 to adjacent end 438 of the collimator 424 in a direction perpendicular to the longitudinal axis 406 (see FIG. 5 ). The radiation shield portions 432, 424 also extend in a direction along the longitudinal axis 406. In certain embodiments, the collimator 424 enables the detector head 404 to be utilized in imaging applications where a radioactive tracer such as I₁₃₁ is utilized. For example with I₁₃₁, the collimator provides adequate collimation for the 364 keV gamma ray and good shielding to reduce eventual contamination from 630 keV into the 364 keV peak (e.g., via limited photopeak charge collection efficiency or patient high energy scattered events). During high energy applications, the thickness of the detector 416 provides some radiation shielding in conjunction with the shielding form the radiation shield 430. In addition, the peripheral CZT pixels act as a shield and absorb some of the gamma rays.

Printed circuit boards 440, 442 for electronics (e.g., power boards) are located in respective cavities 444, 446 formed between the radiation shield 430, the collimators 422, 424, and the semiconductor detector 416. The printed circuit boards 440, 442 flank a portion of the collimator 424 and the semiconductor detector 416. The positioning of the printed circuit boards 440, 442 reduces interference due to non-detecting material. In particular, no interfering material is located on the backside (e.g., anode side) to enable gamma ray collection from both the back and front sides of the detector 416. The printed circuit boards 440, 442, may include dedicated routing blocks and field programmable gate arrays. A printed circuit board 448 including an analog front-end including data channels and ASIC is disposed between the collimator 424 and the semiconductor detector 416. A heat sink 450 is disposed between the collimator 424 and the printed circuit board 448. In certain embodiments, the analog-front end associated data channels and ASIC may be located in the same location as the printed circuit boards 440, 442 and coupled via flex circuitry. In such an embodiment, no heat sink would be disposed between the collimator 424 and the detector 416.

Returning to FIG. 4 , the detector head 400 may be rotated about its longitudinal axis 406 as indicated by arrow 452 to position one of the collimators 422, 424 for use during an imaging scan (i.e., so that the collimator 422, 424 to be used faces the object to be imaged). FIG. 6 is a schematic view illustrating switching between usage of different collimators within a detector head assembly. FIG. 6 depicts a single detector unit 115 of an NM multi-head imaging system. The description of the single detector unit 115 applies to the rest of the detector units 115 of the NM multi-head imaging system. The single detector unit 115 is as described above and includes the detector head 400 as described in FIGS. 4 and 5 having the detector column 404. The detector column 404 includes the detector 416 disposed between the two collimators 422, 424 as described above. The detector unit 116 may move radially in and out as indicated by arrow 454. In addition, the detector head 404 has a sweep motion as indicated by arrow 456. In a first position 455 (e.g., for utilization during a low energy application), the collimator 422 is facing the object to be imaged. In a second position 457 (e.g., for utilization during a high energy application or a dual isotopes application), the collimator 424 is facing the object to be imaged. Utilizing the sweep axis degree of freedom, the detector column 404 may be rotated about its longitudinal axis (e.g., longitudinal axis 406 in FIG. 4 ) approximately 180 degrees (±180 degrees) to change from the first position to the second position or vice versa as depicted in FIG. 6 . Once the detector head 404 is in the desired position (e.g., first or second position), the detector head 404 may be rotated during an image scan a further approximately 105 degrees (±105 degrees). In total, the detector head 404 may rotated up to approximately 285 degrees (±285 degrees). As noted above, the rotation of the detector head 404 occurs via a motor coupled to the detector head 404. The interchanging or switching of the collimators 422, 424 occurs semi-automatically or automatically (e.g., in response to an input or control signal) without removing the collimator 422, 424 from the detector unit 415 and the detector head 400. In certain embodiments, the interchange or switching may be carried out manually.

FIG. 7 is a flow chart of an embodiment of a method 458 for switching between collimators in a detector head assembly of a NM multi-head imaging system. The detector head collimator includes two different collimators configured for different energy applications as described above. One or more steps of the method 458 may be performed by a component of the NM multi-head imaging system (e.g., processing unit 120 in FIG. 1 ). The method 458 includes receiving a receiving an input (e.g., control signal) to change the collimator in the detector head (block 460). The input may be received via an input device of the NM multi-head imaging system. The input may be received in response to selection of a particular imaging scan, a particular radioactive tracer, and a combination thereof. The method 458 also includes rotating (e.g., automatically) the detector column to change the current position of the detector column (e.g., the first position or the second position as described in FIG. 6 ) to another position (e.g., the second position if initially in the first position or the first position if initially in the second position) if the received input necessitates changing the position of the detector head (block 462). The method 458 further includes conducting the scan with the detector column in the desired position (block 464). In certain embodiments, switching between the two different collimators may occur during the same scan (e.g., applications involving dual isotopes (e.g., high and low energy isotopes)).

Embodiments described herein may be implemented in medical imaging systems, such as, for example, SPECT and SPECT-CT. Various methods and/or systems (and/or aspects thereof) described herein may be implemented using a medical imaging system. For example, FIG. 8 is a schematic illustration of a NM imaging system 1000 having a plurality of imaging detector head assemblies mounted on a gantry (which may be mounted, for example, in rows, in an iris shape, or other configurations, such as a configuration in which the movable detector carriers 1016 are aligned radially toward the patient-body 1010). It should be noted that the arrangement of FIG. 8 is provided by way of example for illustrative purposes, and that other arrangements (e.g., detector arrangements) may be employed in various embodiments. In the illustrated example, a plurality of imaging detectors 1002 are mounted to a gantry 1004. In the illustrated embodiment, the imaging detectors 1002 are configured as two separate detector arrays 1006 and 1008 coupled to the gantry 1004 above and below a subject 1010 (e.g., a patient), as viewed in FIG. 8 . The detector arrays 1006 and 1008 may be coupled directly to the gantry 1004, or may be coupled via support members 1012 to the gantry 1004 to allow movement of the entire arrays 1006 and/or 1008 relative to the gantry 1004 (e.g., transverse translating movement in the left or right direction as viewed by arrow T in FIG. 8 ). Additionally, each of the imaging detectors 1002 includes a detector unit 1014, at least some of which are mounted to a movable detector carrier 1016 (e.g., a support arm or actuator that may be driven by a motor to cause movement thereof) that extends from the gantry 1004. In some embodiments, the detector carriers 1016 allow movement of the detector units 1014 towards and away from the subject 1010, such as linearly. Thus, in the illustrated embodiment the detector arrays 1006 and 1008 are mounted in parallel above and below the subject 1010 and allow linear movement of the detector units 1014 in one direction (indicated by the arrow L), illustrated as perpendicular to the support member 1012 (that are coupled generally horizontally on the gantry 1004). However, other configurations and orientations are possible as described herein. It should be noted that the movable detector carrier 1016 may be any type of support that allows movement of the detector units 1014 relative to the support member 1012 and/or gantry 1004, which in various embodiments allows the detector units 1014 to move linearly towards and away from the support member 1012.

Each of the imaging detectors 1002 in various embodiments is smaller than a conventional whole body or general purpose imaging detector. A conventional imaging detector may be large enough to image most or all of a width of a patient's body at one time and may have a diameter or a larger dimension of approximately 50 cm or more. In contrast, each of the imaging detectors 1002 may include one or more detector units 1014 coupled to a respective detector carrier 1016 and having dimensions of, for example, 4 cm to 20 cm and may be formed of Cadmium Zinc Telluride (CZT) tiles or modules. For example, each of the detector units 1014 may be 8×8 cm in size and be composed of a plurality of CZT pixelated modules (not shown). For example, each module may be 4×4 cm in size and have 16×16=256 pixels (pixelated anodes). In some embodiments, each detector unit 1014 includes a plurality of modules, such as an array of 1×7 modules. However, different configurations and array sizes are contemplated including, for example, detector units 1014 having multiple rows of modules.

It should be understood that the imaging detectors 1002 may be different sizes and/or shapes with respect to each other, such as square, rectangular, circular or other shape. An actual field of view (FOV) of each of the imaging detectors 1002 may be directly proportional to the size and shape of the respective imaging detector.

The gantry 1004 may be formed with an aperture 1018 (e.g., opening or bore) therethrough as illustrated. A patient table 1020, such as a patient bed, is configured with a support mechanism (not shown) to support and carry the subject 1010 in one or more of a plurality of viewing positions within the aperture 1018 and relative to the imaging detectors 1002. Alternatively, the gantry 1004 may comprise a plurality of gantry segments (not shown), each of which may independently move a support member 1012 or one or more of the imaging detectors 1002.

The gantry 1004 may also be configured in other shapes, such as a “C”, “H” and “L”, for example, and may be rotatable about the subject 1010. For example, the gantry 1004 may be formed as a closed ring or circle, or as an open arc or arch which allows the subject 1010 to be easily accessed while imaging and facilitates loading and unloading of the subject 1010, as well as reducing claustrophobia in some subjects 1010.

Additional imaging detectors (not shown) may be positioned to form rows of detector arrays or an arc or ring around the subject 1010. By positioning multiple imaging detectors 1002 at multiple positions with respect to the subject 1010, such as along an imaging axis (e.g., head to toe direction of the subject 1010) image data specific for a larger FOV may be acquired more quickly.

Each of the imaging detectors 1002 has a radiation detection face, which is directed towards the subject 1010 or a region of interest within the subject.

The collimators 1022 (and detectors) in FIG. 8 are depicted for ease of illustration as single collimators in each detector head. As noted above, in certain embodiments, each detector unit 1014 (or detector head) includes a detector column that be rotated between two different collimators configured for two different energy applications (e.g., high energy versus low energy). Optionally, for embodiments employing one or more parallel-hole collimators, multi-bore collimators may be constructed to be registered or semi-registered with pixels of the detector units 1014, which in one embodiment are CZT detectors. However, other materials may be used. Registered collimation may improve spatial resolution by forcing photons going through one bore to be collected primarily by one pixel. Additionally, registered collimation may improve sensitivity and energy response of pixelated detectors as detector area near the edges of a pixel or in-between two adjacent pixels may have reduced sensitivity or decreased energy resolution or other performance degradation. Having collimator septa directly above the edges of pixels reduces the chance of a photon impinging at these degraded-performance locations, without decreasing the overall probability of a photon passing through the collimator.

A controller unit 1030 may control the movement and positioning of the patient table 1020, imaging detectors 1002 (which may be configured as one or more arms), gantry 1004 and/or the collimators 1022 (that move with the imaging detectors 1002 in various embodiments, being coupled thereto). A range of motion before or during an acquisition, or between different image acquisitions, is set to maintain the actual FOV of each of the imaging detectors 1002 directed, for example, towards or “aimed at” a particular area or region of the subject 1010 or along the entire subject 1010. The motion may be a combined or complex motion in multiple directions simultaneously, concurrently, or sequentially.

The controller unit 1030 may have a gantry motor controller 1032, table controller 1034, detector controller 1036, pivot controller 1038, and collimator controller 1040. The controllers 1030, 1032, 1034, 1036, 1038, and 1040 may be automatically commanded by a processing unit 1050, manually controlled by an operator, or a combination thereof. The gantry motor controller 1032 may move the imaging detectors 1002 with respect to the subject 1010, for example, individually, in segments or subsets, or simultaneously in a fixed relationship to one another. For example, in some embodiments, the gantry controller 1032 may cause the imaging detectors 1002 and/or support members 1012 to move relative to or rotate about the subject 1010, which may include motion of less than or up to 180 degrees (or more).

The table controller 1034 may move the patient table 1020 to position the subject 1010 relative to the imaging detectors 1002. The patient table 1020 may be moved in up-down directions, in-out directions, and right-left directions, for example. The detector controller 1036 may control movement of each of the imaging detectors 1002 to move together as a group or individually. The detector controller 1036 also may control movement of the imaging detectors 1002 in some embodiments to move closer to and farther from a surface of the subject 1010, such as by controlling translating movement of the detector carriers 1016 linearly towards or away from the subject 1010 (e.g., sliding or telescoping movement). Optionally, the detector controller 1036 may control movement of the detector carriers 1016 to allow movement of the detector array 1006 or 1008. For example, the detector controller 1036 may control lateral movement of the detector carriers 1016 illustrated by the T arrow. In various embodiments, the detector controller 1036 may control the detector carriers 1016 or the support members 1012 to move in different lateral directions. Detector controller 1036 may control the swiveling motion of detectors 1002 together with their collimators 1022. In some embodiments, detectors 1002 and collimators 1022 may swivel or rotate around an axis.

The pivot controller 1038 may control pivoting or rotating movement of the detector units 1014 at ends of the detector carriers 1016 and/or pivoting or rotating movement of the detector carrier 1016. For example, one or more of the detector units 1014 or detector carriers 1016 may be rotated about at least one axis to view the subject 1010 from a plurality of angular orientations to acquire, for example, 3D image data in a 3D SPECT or 3D imaging mode of operation. The collimator controller 1040 may rotate a detector column between two different collimators configured for two different energy applications (e.g., high energy versus low energy).

It should be noted that motion of one or more imaging detectors 1002 may be in directions other than strictly axially or radially, and motions in several motion directions may be used in various embodiment. Therefore, the term “motion controller” may be used to indicate a collective name for all motion controllers. It should be noted that the various controllers may be combined, for example, the detector controller 1036 and pivot controller 1038 may be combined to provide the different movements described herein.

Prior to acquiring an image of the subject 1010 or a portion of the subject 1010, the imaging detectors 1002, gantry 1004, patient table 1020 and/or collimators 1022 may be adjusted, such as to first or initial imaging positions, as well as subsequent imaging positions. The imaging detectors 1002 may each be positioned to image a portion of the subject 1010. Alternatively, for example in a case of a small size subject 1010, one or more of the imaging detectors 1002 may not be used to acquire data, such as the imaging detectors 1002 at ends of the detector array 1006 and 1008, which as illustrated in FIG. 8 are in a retracted position away from the subject 1010. Positioning may be accomplished manually by the operator and/or automatically, which may include using, for example, image information such as other images acquired before the current acquisition, such as by another imaging modality such as X-ray Computed Tomography (CT), MRI, X-Ray, PET or ultrasound. In some embodiments, the additional information for positioning, such as the other images, may be acquired by the same system, such as in a hybrid system (e.g., a SPECT/CT system). Additionally, the detector units 1014 may be configured to acquire non-NM data, such as X-ray CT data. In some embodiments, a multi-modality imaging system may be provided, for example, to allow performing NM or SPECT imaging, as well as X-ray CT imaging, which may include a dual-modality or gantry design as described in more detail herein.

After the imaging detectors 1002, gantry 1004, patient table 1020, and/or collimators 1022 are positioned, one or more images, such as three-dimensional (3D) SPECT images are acquired using one or more of the imaging detectors 1002, which may include using a combined motion that reduces or minimizes spacing between detector units 1014. The image data acquired by each imaging detector 1002 may be combined and reconstructed into a composite image or 3D images in various embodiments.

In one embodiment, at least one of detector arrays 1006 and/or 1008, gantry 1004, patient table 1020, and/or collimators 1022 are moved after being initially positioned, which includes individual movement of one or more of the detector units 1014 (e.g., combined lateral and pivoting movement) together with the swiveling motion of detectors 1002. For example, at least one of detector arrays 1006 and/or 1008 may be moved laterally while pivoted. Thus, in various embodiments, a plurality of small sized detectors, such as the detector units 1014 may be used for 3D imaging, such as when moving or sweeping the detector units 1014 in combination with other movements.

In various embodiments, a data acquisition system (DAS) 1060 receives electrical signal data produced by the imaging detectors 1002 and converts this data into digital signals for subsequent processing. However, in various embodiments, digital signals are generated by the imaging detectors 1002. An image reconstruction device 1062 (which may be a processing device or computer) and a data storage device 1064 may be provided in addition to the processing unit 1050. It should be noted that one or more functions related to one or more of data acquisition, motion control, data processing and image reconstruction may be accomplished through hardware, software and/or by shared processing resources, which may be located within or near the imaging system 1000, or may be located remotely. Additionally, a user input device 1066 may be provided to receive user inputs (e.g., control commands), as well as a display 1068 for displaying images. DAS 1060 receives the acquired images from detectors 1002 together with the corresponding lateral, vertical, rotational and swiveling coordinates of gantry 1004, support members 1012, detector units 1014, detector carriers 1016, and detectors 1002 for accurate reconstruction of an image including 3D images and their slices.

It should be noted that the particular arrangement of components (e.g., the number, types, placement, or the like) of the illustrated embodiments may be modified in various alternate embodiments, and/or one or more aspects of illustrated embodiments may be combined with one or more aspects of other illustrated embodiments. For example, in various embodiments, different numbers of a given module or unit may be employed, a different type or types of a given module or unit may be employed, a number of modules or units (or aspects thereof) may be combined, a given module or unit may be divided into plural modules (or sub-modules) or units (or sub-units), one or more aspects of one or more modules may be shared between modules, a given module or unit may be added, or a given module or unit may be omitted.

As used herein, a structure, limitation, or element that is “configured to” perform a task or operation is particularly structurally formed, constructed, or adapted in a manner corresponding to the task or operation. For purposes of clarity and the avoidance of doubt, an object that is merely capable of being modified to perform the task or operation is not “configured to” perform the task or operation as used herein. Instead, the use of “configured to” as used herein denotes structural adaptations or characteristics, and denotes structural requirements of any structure, limitation, or element that is described as being “configured to” perform the task or operation. For example, a processing unit, processor, or computer that is “configured to” perform a task or operation may be understood as being particularly structured to perform the task or operation (e.g., having one or more programs or instructions stored thereon or used in conjunction therewith tailored or intended to perform the task or operation, and/or having an arrangement of processing circuitry tailored or intended to perform the task or operation). For the purposes of clarity and the avoidance of doubt, a general purpose computer (which may become “configured to” perform the task or operation if appropriately programmed) is not “configured to” perform a task or operation unless or until specifically programmed or structurally modified to perform the task or operation.

As used herein, the term “computer,” “processor,” or “module” may include any processor-based or microprocessor-based system including systems using microcontrollers, reduced instruction set computers (RISC), application specific integrated circuits (ASICs), logic circuits, and any other circuit or processor capable of executing the functions described herein. The above examples are exemplary only, and are thus not intended to limit in any way the definition and/or meaning of the term “computer,” “processor,” or “module.”

The computer or processor executes a set of instructions that are stored in one or more storage elements, in order to process input data. The storage elements may also store data or other information as desired or needed. The storage element may be in the form of an information source or a physical memory element within a processing machine.

The set of instructions may include various commands that instruct the computer or processor as a processing machine to perform specific operations such as the methods and processes of the various embodiments. The set of instructions may be in the form of a software program. The software may be in various forms such as system software or application software. Further, the software may be in the form of a collection of separate programs or modules, a program module within a larger program or a portion of a program module. The software also may include modular programming in the form of object-oriented programming. The processing of input data by the processing machine may be in response to operator commands, or in response to results of previous processing, or in response to a request made by another processing machine.

As used herein, the terms “software” and “firmware” may include any computer program stored in memory for execution by a computer, including RAM memory, ROM memory, EPROM memory, EEPROM memory, and non-volatile RAM (NVRAM) memory. The above memory types are exemplary only, and are thus not limiting as to the types of memory usable for storage of a computer program.

Technical effects of the disclosed subject matter include a radiation detector head assembly of a NM multi-head imaging system that includes two collimators (each specifically configured for use with different energy applications such as high and low energy applications). The disclosed embodiments enable the automatic interchange between the different collimators to occurs within a matter of seconds (e.g., as opposed to minutes). The interchange occurs completely within the radiation detector head assembly (without having to remove one of the detectors) and without the utilization of a mechanical (and manual) collimator exchange process. The quick automatic exchange between collimators saves time during the day and avoids downtime for the imaging system, thus, enabling an improved workflow (e.g., hospital patient flow). The disclosed embodiments may also reduce the cost of the imaging system.

The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

This written description uses examples to disclose the present subject matter, including the best mode, and also to enable any person skilled in the art to practice the subject matter, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

1. A radiation detector head assembly, comprising: a detector column, comprising: a detector having a first surface and a second surface opposite the first surface; a first collimator disposed over the first surface of the detector configured for use during imaging scans involving radiation in a first energy range; and a second collimator disposed over the second surface of the detector configured for use during imaging scans involving radiation in a second energy range different from the first energy range.
 2. The radiation detector head assembly of claim 1, wherein the radiation detector head assembly comprises a motor coupled to the detector column, and the motor is configured to rotate the detector column about a longitudinal axis of the detector column between a first position having the first collimator face towards an object to be imaged and a second position having the second collimator face towards the object to be imaged.
 3. The radiation detector head assembly of claim 2, wherein the motor is configured to rotate the detector column approximately 180 degrees between the first position and the second position.
 4. The radiation detector head assembly of claim 2, wherein the motor is configured to rotate the detector column up to approximately 285 degrees.
 5. The radiation detector head assembly of claim 1, wherein the first collimator and the second collimator have different heights.
 6. The radiation detector head assembly of claim 1, wherein the first surface of the detector comprises a cathode and the second surface of the detector comprises pixelated anodes.
 7. The radiation detector head assembly of claim 6, wherein pixels of the pixelated anodes are registered or semi-registered to collimator holes.
 8. The radiation detector head assembly of claim 6, wherein the detector column comprises a heat sink disposed between the second surface of the detector and the second collimator, and wherein the detector column comprises an analog front end including application specific integrated circuitry disposed between the second surface of the detector and the heat sink.
 9. The radiation detector head assembly of claim 6, wherein the second collimator has a greater height than the first collimator.
 10. The radiation detector head assembly of claim 6, wherein the second energy range is greater than the first energy range or the second energy range partially overlaps with first energy range.
 11. The radiation detector head assembly of claim 1, wherein the detector column comprises a first radiation shield and a second radiation shield flanking both the first collimator and the second collimator.
 12. The radiation detector head assembly of claim 1, wherein the detector column comprises a first printed circuit board for electronics and a second printed circuit board for electronics oriented perpendicular to and flanking the detector.
 13. A nuclear medicine multi-head imaging system, comprising: a gantry defining a bore configured to accept an object to be imaged, wherein the gantry is configured to rotate about the bore; a plurality of detector units mounted to the gantry and configured to rotate with the gantry around the bore in rotational steps, each detector unit configured to sweep about a corresponding axis and acquire imaging information while sweeping about the corresponding axis, wherein each detector unit comprises a detector head comprising: a detector column, comprising: a detector having a first surface and a second surface opposite the first surface; a first collimator disposed over the first surface of the detector configured for use during imaging scans involving radiation in a first energy range; and a second collimator disposed over the second surface of the detector configured for use during imaging scans involving radiation in a second energy range different from the first energy range.
 14. The NM multi-head imaging system of claim 13, wherein each detector unit is configured to change which of the first collimator and the second collimator is utilized during an imaging scan without needing to mount which collimator is utilized.
 15. The NM multi-head imaging system of claim 13, wherein each detector unit is configured to automatically change which of the first collimator and the second collimator is utilized during an imaging scan without removal of the first collimator and the second collimator from the detector unit.
 16. The NM multi-head imaging system of claim 13, wherein the detector unit comprises a motor coupled to the detector column, and the motor is configured to rotate the detector column about a longitudinal axis of the detector column between a first position having the first collimator face towards the object to be imaged and a second position having the second collimator face towards the object to be imaged.
 17. The NM multi-head imaging system of claim 13, wherein the motor is configured to rotate the detector column approximately 180 degrees between the first position and the second position.
 18. The NM multi-head imaging system of claim 13, wherein the motor is configured to rotate the detector column up to approximately 285 degrees.
 19. The NM multi-head imaging system of claim 13, wherein the first surface of the detector comprises a cathode and the second surface of the detector comprises pixelated anodes.
 20. A method for changing a collimator in a detector head of a nuclear medicine (NM) multi-head imaging system, comprising: receiving an input to change the collimator in the detector head of the NM multi-head imaging system; and rotating a detector column from a first position to a second position or a second position to a first position in response to the input, wherein the detector column comprises a detector having a first surface and a second surface opposite the first surface, a first collimator disposed over the first surface of the detector configured for use during imaging scans involving radiation in a first energy range, and a second collimator disposed over the second surface of the detector configured for use during imaging scans involving radiation in a second energy range different from the first energy range. 